1. Field of the Invention
The present invention relates to the field of Data Communication. More specifically, the present invention relates to bridging communication endpoints that employ Integrated Services Digital Network (ISDN) compliance data circuit terminating equipments (DCEs) and communication endpoints that employ Simultaneous Voice and Data (SVD) enabled data circuit terminating equipments (DCEs).
2. Background Information
A communication endpoint employing an ISDN compliance DCE (hereinafter ISDN endpoint) having a Low cost Basic Rate Interface (BRI) ISDN adapter supports two ISDN bearer or B-channels. A BRI ISDN adapter allows a data call to be placed on one channel and a voice call to be placed on the other channel. Normally, International Telecommunication Union - Telecommunication Standardization Sector (ITU-T) Recommendation V.120 error correction protocol is employed to provide error free data communication. A user may engage in a voice call with a traditional analog telephone endpoint, or a voice and/or data call with another ISDN endpoint, thereby allowing the user to engage in applications such as personal conferencing that require a data channel for data transmission and a voice channel for voice transmission with the other ISDN user.
On the other hand, a communication endpoint employing a SVD enabled DCE (hereinafter a SVD endpoint) has only one analog telephone line. The SVD enabled DCE is capable of making only one call. However, the SVD enabled DCE is capable of operating in multi-modes, including a voice only mode, a SVD mode and a data only mode. When operating in the SVD mode, voice and data are multiplexed over two logical connections established for the single call, for example logical channels 31 and 0 of a ITU-T V.42 modem connection. Thus, the SVD enabled DCE is nevertheless capable of making either a voice call with a traditional analog phone endpoint or a voice and/or data call with another similarly equipped endpoint, thereby also allowing the user to engage in applications such as personal conferencing that require a data channel for data transmission and a voice channel for voice transmission with the other SVD user.
Since low cost ISDN compliance DCEs are not designed with modem emulation capability, and SVD enabled DCEs are not designed to engage in two calls over two channels, ISDN and SVD endpoints are unable to connect to each other. Thus, it is desirable to bridge these two types of communication endpoints. As will be disclosed in more details below, the present invention provide a method and apparatus for bridging ISDN and SVD endpoints that achieve these and other objectives.
For further information on SVD calls, see copending U.S. patent application Ser. No. 08/265,455, filed on Jun. 24, 1994, entitled Method and Apparatus For Making A Multi-Modal Voice And/or Data Call Over A Single Analog Telephone Line, assigned to the assignee of the present invention.